Orthotitanic compound used in method for improving wet strength of paper and resulting paper



Paul Lagally, Pleasant Gap, Pa., assignor to Linden Laboratories, lnc., State College, Pa., a corporation of Pennsylvania No Drawing. Filed June 15,1956, Ser. No.- 591,531

This invention relates to improved papers and'in particular to novel papers having improved wet strength. The invention also relates to improved papers containing fillers in which there are uniform distribution of the fillers throughout the papers.

In many uses of paper it is essential that the-paper possess a high wet strength, such as packaging paper for meat, hand towels, garbage bags, sand paper backings, adhesive tape backings, etc. Papers used-for the aforementioned purposes often come in contact with moisture and must be sufiiciently resistant thereto so as, not to rapidly deteriorate in use.

Papers to be used as printing papers in general should possess the characteristics of surface smoothness, whiteness, printability and opacity.

Prior to the present invention various techniques have been used for improving the characteristics of paper. Forv example, the addition of fillers to paper pulp toimprove the surface, smoothness, whiteness, printability and opacityv of the paper sheet is well known. Unfortunately, however, it is not always possible to obtain adequate retention of the filler by the pulp and/ or uniform distribution of the filler throughout the paper sheet,

Objects and advantages of the inventionwill be setforth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attainedby means of the processes, steps, combinations, improvements and compositions pointed out in the appended claims.

The invention consists in the novel processes, steps, combinations and improvements, and compositions herein shown and described.

it is an object of this invention to provide improved papers having the characteristics of high wet tensile strength. A still further object of this invention is to provide improved papers having fillers incorporated there in wherein there is a high retention of filler by the paper fibers and in which the filler is uniformly distributed throughout the paper. A still further object of this invention is to provide novel methods for the production of improved papers having the characteristics set forth in accordance with the foregoing objects.

It has been found that the foregoing objects may be realized by producing paper from paper pulp utilizing water soluble solutions of reactive titania in the paper pulp. By reactive titania is meant monomeric orthotitanic acid of the structure Ti(OI-l) or a low polymer )4]n' In accordance with one aspect of the present invention, it has been found that the incorporation of a water soluble solution of reactive titania to a dilute paper stock (slurry of pulp), followed by subsequent drying of said pulpto form a paper sheet, results in the formation of a paper sheet having improved wet tensile strength.

Moreover, it has also been found that if the paper stock contains a filler, the reactive titania increases the'retention of the filler by the paper pulp and gives a more uniform distribution of the filler throughout the paper. Advantageously, the filler-containing papers produced in ac cordance with this invention are free of two-sideness, i.e., presence of more filler on one side of the sheet than-the other, because of the uniform distribution of the filler throughout the paper sheet.

States atent 'ice The water soluble reactive titania solutions useful in accordance with this invention can be prepared from a water soluble orthotitanic ester in the presence of a suitable screener to delay hydrolysis of the orthotitanate, thus producing a. highly reactive form of monomeric or low polymer orthotitanic acid. These stabilized solutions are disclosed in copending application Serial No. 576,498 filed April 5, 1956, by Paul Lagally and is now Patent 2,950,174. The orthotitanates disclosed in Patent 2,950,- 174 are those which arerclatively stable in aqueous medium and which require a hydrolyzing agent, such as an acidor an alkali, for hydrolysis thereof. Examples of the preferred orthotitanates of this type are those of the chelated kind.

The water soluble reactive titania solutions useful in accordance with this invention can be prepared from a water-soluble orthotitanic ester in the presence of a suitable screeneras illustrated by esters containing:

(1) Two, three or four ligands containing basic nitrogen. Chelated esters of this type are, for example, isopropyl-tri-triethanolamine orthotitanate, di-isopropyl-ditriethanolamine orthotitanate, di-isopropyl-di-diethanolamine orthotitanate, tetra cyanoethyldiethanolamine orthotitanate.

(2) Less than two ligands containing basic nitrogen andin addition other ligands containing electron-donating groups. Water-soluble esters or this type are, for example, tri-cyano-ethyl-mono-triethanolamine orthotitanate, tri ethyleneglycol-monotriethyleneglycol mono triethanolamine orthotitanate.

As indicated heretofore, orthotitanates which are relatively stable iii-aqueous medium and of the type indicated by the preferred esters require the addition of a suitable'hydrolyzing agent for the hydrolysis thereof to occur; Moreover, the hydrolyzing agent must be of such nature that it will not form a stable titanium complex with the hydrolyzed product.

Examples of acids which are not useful as hydrolyzing agents because they form stable titanium complexes are- (1)hydroxy acids containing a hydroxy group in the alpha or beta position such as lactic acid or tartaric acid: (2) lower aliphatic dicarboxylic acids such as oxalic acid and malonic acid and (3) hydro-fiuoric acid.

Specific examples of acids which may be used as a hydrolyzing agent are:

Acid Formula Hydrochlcnm H01 Acetic, CHsCOOH TllfitlOlOflCQlllG- CFSCOOH Perfluorobutyri O F COOH Cyanoaeetic. CH2CNCOOH Chloroacetie. 01120 100011 Triehloroacetic 0 C 0 OH Maleict (CHCOOHM Succimm (CHZCOOHM Polyncryllcu (CHzCHCOOI-I)n Thmglycohc, CHZCOOH Thiornalic OHZCOOH 0 SEC 0 OH Garboxynlethyl-mereaptosuceinie 011120 0 OH Si GHCOOH CH2COOH Toluenesulfonic CH3C5H1SO H Sulfanillc NH O5H4SO3H In addition .to acids, bases may be used as hydrolyzing agents for certain of the orthotitanates. Examples of suitable bases for this purpose are sodium hydroxide, potassium hydroxide and nitrogen containing bases such as ammonium hydroxide, ethyl amine, diethyl amine, pyridine, piperidine and cyclohexylamine.

As indicated heretofore, a stabilizer is employed for controlling the hydrolysis of the orthotitanate and for preventing the precipitation of the hydrolyzed product from the aqueous solution. The stabilizer contains electron donating groups for temporarily screening the orthotitanic acid or ester to prevent polymerization thereof and subsequent precipitation from solution. Hence, any compound exhibiting the required electron donating qualities for eifeotuating the desired screening effect may be used as the stabilizer.

Typical compounds which may be used as stabilizers include hydroxyaldehydes and hydroxy-ketones and corresponding semiacetals of the aldehydes and ketones. Examples of such compounds are the monosaccharides such as glucose, fructose, mannose, xylose, threose, erythrose, rhamnose; the polysaccharides such as lactose and cellobiose, sugars with straight chains or as substances having oxide rings such as methyl glucoside may also be used. Also, suitable as stabilizers for this purpose are watersoluble alcohols as represented by those having straight chain or cyclic structure such as ethylene glycol, diethylene glycol, triethylene glycol, sorbitol, mannitol and inositol. Also, operable are water soluble amides such as urea, dimethylforamide; hydroxy-alkyl derivatives of aminos containing tertiary nitrogen such as triethanolamine and hydroxyalkyl-alkylenepolyamines such as tetrahydroxyethyl ethylene diamine.

In addition to the aforementioned stabilized watersoluble reactive titania solutions, Water-soluble reactive titania solutions can also be used which are prepared from certain water-soluble orthotitanate esters by neutralization of an aqueous solution of the ester to give a product which is not stable for long periods of time but for short intervals, long enough to be used on a practical basis. Examples of orthotitanates which may be used for this purpose are:

Tetra-triethanolamine orthotitanate Tetra-diethanolamine orthotitanate Isopropyl-tri-triethanolamine orthotitanate D-iisopropyl di-triethanolamine orthotitauate Dicyanoethyl-di-triethanolamine orthotitanate Tetra-aminoethauolamine orthotitanate Tetra-diethylethanolamine orthotitanate In general, the procedure used in accordance with this invention involves addition of reactive titania solution to a slurry of pulp (dilute stock containing cellulose fibers and which may contain filler in water, followed by formation of the paper sheet; or addition of a Water-soluble orthotitanate ester to the stock followed by hydrolysis of the ester by a suitable hydrolyzing agent to reactive titania, followed by formation of the paper sheet. The addition of the reactive titania alone imparts wet strength to the sheet, but the efiect may be further increased by heating after formation and drying.

The amount of titania used will vary depending upon the structure of the orthotitanate used for making the reactive titania. A high molecular weight compound is most practical where a lower retention for wet strength is desired but where higher retentions (high wet strength) are desired, the esters of lower molecular weight are preferred. The retention of small amounts of titania is al-. most quantitative but when amounts greater than 2.9% Ti(OH) (2% TiO based on the weight of dry pulp are used, the retention is not quantitative and the unused titania remains in solution.

In general, the range of concentration of Ti(OH) will vary between 1 to 45%, and preferably 1 to 20%. As,

indicated hereinabove, when amounts of greater than i 2.9% are used the retention of the titania by the cellulose fibers is not quantitative. When the pulp contains a filler, an amount as high as 5% may be retained quantitatively, a portion of which is retained by the cellulose fibers and a portion by the filler.

As indicated heretofore, it has been found that sheets formed from paper pulp containing fillers in accordance with this invention exhibit increased retention of fillers and a lack of two-sidedness. Any suitable conventional paper filler may be used, such as clay, calcium carbonate, titanium oxide, silica, etc. In general, the filler is in an amount from to 45% based on the dry weight of the pulp.

Aqueous solution of wet strength agent consisting of a titanium containing agent selected from the group consisting of monomeric orthotitanic acid and water-soluble, low moleculan weight; polymers of orthotitanio acid Slurry of paper pulp containing cellulose fibers Forming paper sheet in conventional manner Drying formed sheet In order to illustrate the invention more specifically the following examples are given hereinbelow. Unless otherwise indicated, the percentages or parts given are by weight.

The following Examples I-IV disclose the preparation of stabilized water soluble orthotitanate solutions which may be used as the source of reactive titania in accordance with the present invention.

EXAMPLE I EXAMPLE II 120 grams of a mixture of 1 mole tetra isopropyl orthotitanate and two moles triethanolamine (containing .206 mole di-isopropyl-di-triethanolamine titanate) are dissolved in 200 ml. water and 200 of a 50% solution of urea are added. The resulting mixture is neutralized with 2 5 ml. cone. H01 and diluted with water to 600ml.

EXAMPLE III To 10 grams of a mixture of one mole tetra-isopropylorthotitanate and four moles triethanolamine (0.0131 mole tetra-triethanolarnine titanate) are added 3.9 grams triethanolamine (0.026 mole) .20 ml. of water are added and, after neutralization, the obtained solution is diluted with water to 50 ml. The obtained mixture remains stable.

precipitates insoluble titania quickly. EXAMPLE IV EXAMPLE V To a semi-bleached kraft pulpofs600cc. (S..-R.) freeness basis weight (24" x 36'. x 480:30 lbs.) was added an amount ofmethyl glucosidestabilized.diisopropyl-ditriethanolamine titanate of Example I to give 3.2% Ti(OH) based on the dry weight of pulp. The sheet was then formed in a standard T.A.P.P.I. sheet mold. Measurement of the Wet tensile showed it to be 1.8 pounds per inch before heating and 3.8 pounds per inch after heating one minute at 350 F. A sheet formed in the same manner without titania compound present would have a wet tensile of less than .1 pound/ inch.

EXAMPLE VI To Duracel pulp of 700 cc. freeness (S.R.) basis weight (24" x 36" x 480:30 lbs.) was added an amount of methyl glucoside stabilized diisopropyl di-triethanolamine titanate of Example I calculated to give 33% Ti(OH) based on the dry weight of pulp. After formation of the sheet and drying, the Wet tensile strength was found to be 2.4 pounds per inch.

EXAMPLE VII In the same manner as described in Example V, a quantity of methyl glucoside stabilized diisopropyl ditriethanolamine titanate of Example I was added in an amount calculated to give 17% Ti(OH) based on the weight of dry pulp. The resulting sheet when tested gave 46 pounds per inch wet tensile before heating and 7 pounds per inch after heating one minute at 350 F.

EXAMPLE VIII To Duracel pulp of 700cc. freeness (S.R.) basis weight (24 X 36" x 480:30 lbs.) was added a quantity of di isopropyl di-triethanolamine titanate calculated to give 6.8% Ti(OH) based on dry weight of pulp. The mixture was then neutralized to pH 7 with dilute hydrochloric acid. After forming the sheet and drying, the wet tensile strength was determined to be 1 pound per inch.

EXAMPLE IX In the same manner as in Example VIII, a quantity of diisopropyl di-aminoethylethanolamine titanate calculated to give 12% Ti(OH) based on dry weight of pulp gave 2.2 pounds per inch wet tensile before heating and 2.8 pounds per inch after heating.

EXAMPLE X In the same manner as in Example VIII, a quantity of diisopropyl di-diethanolmethyl amine titanate calculated to give 11% Ti(OH) gave 4.4 pounds per inch wet tensile before heating and 5.4 pounds per inch after heating.

In the same manner as in Example VIII, additional sheets were prepared, using the ingredients and having the properties indicated in below Table I.

ized aqueous solution of tetra-triethanolamine titanate Table I Percent TKOH); Wet Wet Compound Based'on Tensile, Tensile Dry lbs/in. after Weight Heating, of Pulp lbs/in;

Ex. XI Tetra-E thanoldiethyl- 8 4 5. 3

amine Titanate. Ex. XII Tetra-Triisopropanol- 6 4. 2 5. 3

amine Titanate. Ex. XIII Tetra-D.iisopropanol;v 8 3. 6 4. 8.

amine Titanate. Ex. XIV.. Tetra-Dietliylamlncg 14 1. 5 1. 7

Titanate.

The following examples XV toXVII serve todisclose the preparation of paperv sheets containing fillersin ac cordance with this invention.

EXAMPLE XV- To cellulose pulp from type ordinarily used for book papers (60% soda, 25% sulfite, 15% old paper) 015.600 cc. Schopper-Riegler freeness basis weight including filler (24" x 36" x 480: lbs.) at 2% consistency was added 10% filler suspension (clay) to give 30% filler based on dry weight of pulp. To this slurry was added a quantity of urea stabilized di-isopropyl di-triethanolamine titanate of Example I to give 2% Ti(OH) based on dry weight of pulp. The pulp was diluted to .5% consistency and the sheet formed. Filler retention was found to be 70% determined by ash content of the finished sheet. A sheet made in the same manner but using no reactive titania showed filler retention to be only 30%.

EXAMPLE XVI To cellulose pulp from the type ordinarily used for book papers 60% soda, 25% sulfite, 15% old paper) of 600 cc. Schopper-Riegler freeness basis weight including filler (24" x 36" X 480:100 lbs.) was added a 10% filler suspension (CaCO to give 30% filler based on dry weight of pulp. To this slurry was added a quantity of methyl glucoside stabilized di-isopropyl ditriethanolamine titanate of Example I to give 1% Ti(OH) based on dry weight of pulp. The pulp was diluted to .5 consistency and the sheet formed. Filler retention was found to be 81% determined by ash content. A sheet made similarly but using no reactive titania showed filler retention to be only 22%.

EXAMPLE XVII To cellulose pulp of the same type used in Example XVI was added a 10% filler suspension (clay) to give 30% filler based on dry weight of pulp. To this slurry was added a quantity of methyl glucoside stabilized di-isopropyl ditriethanolamine titanate of Example I to give 1% Ti(OH)., based on dry pulp weight. The titania compound was then neutralized to pH 6 with dilute hydrochloric acid, and the pulp diluted to .5 consistency. The sheet was then formed. Filler retention was found to be 89.0% as determined by ash content. A sheet made without titania present showed filler retention to be only 8.7%.

The invention in its broader aspects is not limited to the specific steps, processes, compositions, combinations and improvements shown and described, but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

The present application is a continuation-in-part of application Serial No. 576,498, filed April 5, 1956, now U.S. Patent No. 2,950,174.

What is claimed is:

1. A paper sheet having improved wet strength comprising cellulose fibers held together by a wet strength agent consisting of a titanium containing agent selected from the group consisting of monomeric orthotitanic acid and water-soluble, low molecular-weight polymers of orthotitanic acid, said titanium containing agent being in an amountfrom about 1 to 45% by weight based on the dry weight of fibers.

2. The method of forming a paper sheet having improved Wet tensile strength comprising the steps of mixing with a slurry of paper pulp including cellulose fibers, an aqueous solution of a wet strength agent consisting of a titanium containing agent selected from the group consisting of monomeric orthotitanic acid and watersoluble, low molecular-weight polymers of orthotitanic acid, said titanium containing agent being in an amount from about 1 to 45% by weight based on the dry weight of fibers.

3. A paper sheet containing a filler uniformly dis tributed throughout comprising cellulose fibers and a filler held together by a Wet strength agent consisting of a titanium containing agent selected from the group consisting of monomeric orthotitanic acid and water-soluble, low molecular-weight polymers of orthotitanic acid, said titanium containing agent being in an amount from about 1 to 45 by weight based on the dry weight of fibers,

4. The method of forming a paper sheet containing a filler uniformly distributed throughout comprising the steps of mixing with a slurry of paper pulp comprising cellulose fibers and filler, an aqueous solution of a Wet strength agent consisting of a titanium containing agent selected from the group consisting of monomeric orthotitanic acid and water-soluble, low molecular-weight polymers of orthotitanic acid, said titanium containing agent being in an amount from about 1 to 45% by weight based on the dry weight of fibers.

References Cited in the tile of this patent UNITED STATES PATENTS 2,345,985 McKinney Apr. 4, 1944 2,378,193 Cummins June 12, 1945 2,564,365 Kingsbury Aug. 14, 1951 2,579,413 Boyd Dec. 18, 1951 2,643,262 Bostwick June 23, 1953 2,680,108 Schmidt June 1, 1954 2,689,858 Boyd Sept. 21, 1954 2,721,787 Hettrick Oct. 25, 1955 2,749,248 Benson June 5, 1956 2,785,995 Kress Mar. 19, 1957 2,824,114 Bostwick Feb. 18, 1958 2,930,106 Wrotnowski Mar. 29, 1960 

1. A PAPER SHEET HAVING IMPROVED WET STRENGTH COMPRISING CELLULOSE FIBERS HELD TOGETHER BY A WET STRENGTH AGENT CONSISTING OF A TITANIUM CONTAINING AGENT SELECTED FROM THE GROUP CONSISTING OF MONOMERIC ORTHOTITANTIC ACID AND WATER-SOLUBLE, LOW MOLECULAR-WEIGHT POLYMERS OF ORTHOTITANIC ACID, SAID TITANIUM CONTAINING AGENT BEING IN AN AMOUNT FROM ABOUT 1 TO 45% BY WEIGHT BASED ON THE DRY WEIGHT OF FIBERS. 